This invention relates to video signal processing and, more particularly, to a digital signal processor for use with chrominance signals which are developed in a color video system.
In the conventional transmission of analog color television signals, chrominance signals are transmitted using a narrower bandwidth than the bandwidth for the luminance signal to capitalize on one characteristic of visual perception. Namely, the eye has less resolution to changes in a color television scene produced by the chrominance signal than those produced by the luminance signal. This technique is used in the various arrangements for generating different forms of total video signals each including a luminance signal and one or more chrominance signals such as, for example, those used in the NTSC, SECAM and PAL systems of video color transmission.
The principle of this technique and other techniques exploiting different characteristics of visual perception have also been utilized in the newer field of digital coding of color signals for transmission. For example, one technique is to code the luminance and individual chrominance signals each separately and, accordingly, to different degrees of accuracy or resolution. However, what has not been appreciated and/or exploited heretofore is that a negative orthogonal correlation exists between luminance and chrominance signals. Within the total video signal generated by conventional processing of a typical television scene, the occurrence of high density luminance variations along a horizontal scan line is often accompanied by a low density of chrominance variations in the vertical or orthogonal direction between corresponding picture elements from one scan line to vicinal scan lines. Fortunately, the converse situation also occurs.
An object of the present invention is to reduce the amount of information required to transmit a broadcast quality color signal using signal processing techniques that also serve to minimize fluctuations in information content of the total video signal.
A related object is to increase the information efficiency of a total video signal by exploiting the abovementioned relationship between luminance and chrominance signals.
Another object is to code chrominance signals using interpolation techniques that provide increased resolution to large edge changes of chrominance components while reducing the quality of fine detail to which visual perception has low resolution.